1. Field of the Invention
The present invention relates to antibacterial agents for mammals comprising as effective ingredients cephalosporin compounds having 2-(2-aminothiazol-4-yl)-2{(1S)-carboxyethoxyimino}acetyl group on the side chain at the 7-position thereof and 1-ethylpyridinium-4-ylthiomethyl group on the side chain at the 3-position thereof or non-toxic salts thereof.
2. Prior Art
.beta.-Lactam antibacterial agents represented by penicillin and cephalosporin have been widely used for mammals including human. A current serious problem from a clinical viewpoint is appearance of bacteria which are resistant to .beta.-lactam antibacterial agents caused by frequent use of .beta.-lactam anti-bacterial agents.
In recent years, cephalosporins effective for these resistant bacteria have been investigated and compounds having a .alpha.-dimethylcarboxymethoxyiminoaminothiazoleacetic acid on the side chain at the 7-position thereof and showing potent activity against Pseudomonas aeruginosa are disclosed in West German Pat. No. 2,921,316. On the other hand, cephalosporins having a more wider and potent antibacterial activity against resistant Gram-positive and Gram-negative bacteria are disclosed in Published Unexamined Japanese Patent Application No. 192394/82. A common characteristic of these compounds is that pyridine or a substituted pyridine is bound to the 3'-position of cephalosporin in the form of quaternary salt on the side chain at the 3-position thereof.
A problem in investigations on an enhanced antibacterial agent of cephalosporin including these prior art lies in that when the antibacterial activity is enhanced against Gram-positive bacteria, the antibacterial activity against Pseudomonas aeruginosa is reduced, whereas when the antibacterial activity against Psuedomons aeruginosa is enhanced, the antibacterial activity against Gram-positive bacteria is reduced.
In order to solve the problem, the present inventors prepared cephalosporin compounds having the asymmetric center on the alkoxy moiety of .alpha.-alkoxyiminoaminothiazoleacetic acid present on the side chain at the 7-position and having 1-alkyl-pyridinium-4-ylthiomethyl group at the 3-position which are effective against bacteria including a wide range of resistant bacteria and filed a patent application directed thereto as Japanese Patent Application No. 267984/85 (Japanese Laid-open Patent Publication No. 126189/87). Subsequently, the present inventors have made investigations on the stereochemistry of the alkoxyimino moiety and on the alkyl moiety of 1-alkyl-pyridinium-4-ylthiomethyl group against resistant bacteria, made tests for antibacterial activity in more detail and made animal tests in a wider range, and provided with more practicable compounds as antibacterial agents for mammals including human to solve the problem.